score=int(input("成绩:"))
def ll(score):
    if score>=90 and score<=100:
        return "A"
    elif score>=80 and score<90:
        return "B"
    elif score>=70 and score<80:
        return "C"
    elif score>=60 and score<70:
        return "D"
    else:
        return "E"
ll(score)
print(ll(score))